drm/i915: Nuke drm_driver irq vfuncs

Stop using the irq vfuncs under drm_driver. That's not going to fly
in a mixed gen environment since the structure is shared between all
the devices.

v2: Allow intel_irq_uninstall() to be called twice due to
    intel_modeset_cleanup() calling it as well. Toss in a
    FIXME to remind us that this is not great.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190620103334.15651-1-ville.syrjala@linux.intel.com


Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>